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Biofuels in lime kilns • Operating experience in the Nordic pulp and paper industry, TAPPI Journal October 2024
ABSTRACT: The lime reburning process is a central part of the chemical pulp mill. It is energy intensive and consumes large amounts of fossil fuel, globally consuming about 50 terawatt-hours (TWh) of fuel per year. Conversion to operation with biofuel is interesting, both to reduce carbon dioxide emissions and to reduce costs. Researchers interviewed managers in mills that use solid, liquid, or gasified biofuels to replace fuel oil or natural gas in their lime kilns, and they conducted surveys related to fuel consumption and operations and maintenance. In Sweden and Finland, there were ten mills in 2020 using biomass powder or gasified biomass as the primary fuel, and two more installations were under construction. There were also nine installations in operation or under construction outside the Nordic countries. Fourteen mills in Sweden and two mills in Finland used tall oil pitch as the main fuel. Fuel consumption in Swedish lime kilns was 3.8 TWh in 2020, and 90% of this energy was supplied with biofuels. Of about 4.2 TWh used in Finnish lime kilns, approximately 45% was supplied with biofuels. Developments in the design of the fuel supply system include belt dryers being used in all new installations and mass flow metered dosing systems being used in most new pulverized fuel installations. Bark gasifiers have increased considerably in size. Lignin powder firing has been established as a proven option. A solution for many Swedish and Finnish mills is the use of tall oil pitch as a replacement for fuel oil.
Journal articles
Magazine articles
Model development for real oxygen delignification processes, TAPPI Journal October 2024
ABSTRACT: Previous extensive work has been done on modeling the oxygen delignification process, based on how the basic parameters, i.e., temperature, kappa number, concentration of alkali, and concentration of oxygen, affect the delignification rate. However, these models are not used extensively to evaluate the performance of real processes, primarily because they have not been able to properly consider all the essential issues affecting delignification in practice. Such issues include the mass transfer and consumption of oxygen, which defines the concentration of dissolved oxygen in the process, and the effect of that concentration on the delignification rate. In this paper, a new way to model the oxygen delignification process is used in which these parameters, among other smaller matters, are taken into account. The basic model and its parameters were defined by the information obtained from the literature, delignification made in the laboratory tests, and mill processes and mill tests. An essential aspect of these studies was the information obtained from the oxygen concentration measured in the residual gas obtained from the top of the reactor. With the aid of this measurement, it was possible to define more accurately the consumption of oxygen and partial pressure of oxygen that define the concentration of dissolved oxygen in the reactor. Using mill experiments, a model was formed that predicts the operation of the oxygen delignification process. The model was used to show how much the process could be improved by optimizing the charge of the oxygen. The mill experiments also confirmed that mass transfer of oxygen is modeled correctly enough, except when the charge of oxygen is very low and/or the mixing is not efficient enough. In that case, there is variation in the concentration of oxygen in the process that should be taken into account in the modeling.
Journal articles
NIRS determination of carbohydrates from hydrothermal-treated rice straw, TAPPI JOURNAL April 2012
NIRS determination of carbohydrates from hydrothermal-treated rice straw, TAPPI JOURNAL April 2012
Journal articles
Alkaline xylan extraction of bleached kraft pulp â?¢ effect of extraction time on pulp chemical composition and physical properties, TAPPI JOURNAL April 2012
Alkaline xylan extraction of bleached kraft pulp • effect of extraction time on pulp chemical composition and physical properties, TAPPI JOURNAL April 2012
Journal articles
Increasing lime production while decreasing kiln pluggage through installation of the first LimeFlash lime kiln feed system in North America, TAPPI JOURNAL August 2012
Increasing lime production while decreasing kiln pluggage through installation of the first LimeFlash lime kiln feed system in North America, TAPPI JOURNAL August 2012
Journal articles
The sulfite mill as a sugar-flexible future biorefinery, TAPPI JOURNAL August 2012
The sulfite mill as a sugar-flexible future biorefinery, TAPPI JOURNAL August 2012
Journal articles
Fiber interaction with a forming fabric, TAPPI JOURNAL August 2012
Fiber interaction with a forming fabric, TAPPI JOURNAL August 2012
Journal articles
Optical analysis of ink and other contaminants in process waters, TAPPI JOURNAL August 2012
Optical analysis of ink and other contaminants in process waters, TAPPI JOURNAL August 2012
Journal articles
Process control for stickies, TAPPI JOURNAL February 2012
Process control for stickies, TAPPI JOURNAL February 2012
Journal articles
Conference review: Recycling sessions at TAPPI PEERS, TAPPI JOURNAL February 2012
Conference review: Recycling sessions at TAPPI PEERS, TAPPI JOURNAL February 2012